Roast Chicken “stuffed under the skin”

Name: Roast Chicken “stuffed under the skin”
Ingredients: Serves 4; 1 free-range chicken (about 3 1/2 lbs); Salt and pepper; 2 cloves garlic, chopped; 2 shallots, chopped; 2 ounces wild mushroom, chopped; 1/2 cup chestnuts, cooked and chopped; 1/4 cup pine nuts, toasted and chopped; 1 black truffle, cleaned and chopped (optional); 1/4 cup cognac; 1 1/4 cup panko; 1/4 cup herbs, such as parsley, chives and chervil, chopped; 8 ounces butter, softened; 2 tablespoons flour; 2 cups chicken stock